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TESTING MANIJAl 

BACTERIAL 
CONTROL GLIDE 



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Farm Products Co.»In 



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BOOK Noi47 



THIS BOOK IS THE PROPERTY 

of 

Borden's 

Farm Products Co., Inc. 



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Copyright, 1919 
by . 
William H. Marcussen 



FtD -1 1920 



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PREFACE 

While a number of text books, experiment station bulletins, 
etc., give more or less complete directions for carrying out the 
Babcock test for butter fat, none of these works cover in detail 
the matter of conducting the test in quantities, as is the practice 
in country milk stations where composite samples are taken. 
This manual has been prepared after a careful study of the com- 
mon irregularities that enter into this work and is designed for 
the purpose of aiding the Borden operators in their daily work, 
not only as to accuracy, but in saving of time and labor as well. 

In the printed pages which follow, will be found the personal 
experience of the undersigned in visiting and instructing local 
testers in their work and in each and every case the suggestions 
outlined must be carefully followed in order that a standard 
practice of efficiency be maintained in this class of work. 

Borden's Farm Products Co., Inc. 

Wm. H. Marcussen. 

April 28, 1917. 

PREFACE TO REVISED EDITION 

In order to keep abreast of the times in the testing of dairy 
products, several corrections and additions to the original text 
have appeared necessary and they have been incorporated in this 
revised edition of this little book. 

The increasing importance of the subject of bacteria and 
their relation to the milk supply, as indicated by the interest 
shown along these lines by state and municipal Departments 
of Health and other sanitarians, together with a recognition 
on the part of progressive milk distributors that this problem 
mast be successfully solved, has prompted including in this re- 
vised edition, standard directions for the collection and prepa- 
ration of samples of milk for bacterial examination. 

Wm. H. Marcussen. 
September 17, 1919. 



CONTENTS 

Milk Page 

Sampling of Milk. Collection of Composite Samples ... 7 

Composite jars. Marking of jars. Composite jar 
cabinet. Taking of sample. Preservative. Care 
of Composite samples. 

Preparation of Sample for Testing 8 

Testing days. Testing equipment. Mark of certi- 
fication. Warming of composite samples. Loosing 
butter fat from jar. Pipette sample. Cooling 
sample to 60 degrees F. Rinsing pipette. 

Acid 10 

Purpose of acid. Adding the acid. Color forma- 
tion in acid and milk. Handling very strong acid. 

Centrifuging Test Bottles 12 

Temperature of Fat Column 13 

Reading the Fat Column 13 

Reason for so reading. Column within graduated 
neck. When to check results. Record of results. 

Appearance of Completed Test 15 

Color. Black specks. Light colored specks. Gas 
bubbles. 

Cleaning Babcock Glassware 15 

Legislation on Testing 16 

Testing Abnormal Milk 18 

Frozen milk. Sour milk. Churned milk. 
Conclusions 18 

Cream 20 

Sampling cream. Weighing cream sample. Cream test 
bottles. Babcock test. Amyl alcohol test. Tem- 
perature of fat column. Flattening the meniscus. 

Skim Milk 24 

Butter 25 

Preparation of sample. Testing for butter fat. 
Testing for moisture. Computing overrun. Fat 
test on buttermilk. Computing loss of fat in 
buttermilk. 



CONTENTS— Continued 

Page 
Cheese 29 

Testing for butter fat. Testing for moisture. 
Cheese -yield. Actual yield. Yield per pound 
butter fat. 

Plain Condensed Milk 34 

Acidity of Milk or Cream 35 

Lactometer 37 

Board of Health type. Quevenne type. Precau- 
tions in using lactometer. Calculations of total 
solids. 

Standard Testing Equipment 39 

Standardizing 40 

Methods. Tables for 20%, 38% and 40% cream. 

Questions and Answers on Testing 46 

Blank Pages 52 

For inserting additional material on testing. 

Bacterial Control 78 

Direct Microscopic Method 78 

Detection of High Count Dairies 78 

Directions for Preparing Smears by Country Shipping 

Stations 79 

Collection of samples. Sample tray. Making the 
smears. Guide slide. Measuring milk for smears. 
Rinsing pipette. Drying smears. Cleaning and 
sterilizing vials. Report of results. 

Corrective Work 83 

Essentials for Low Bacteria Count Milk 84 

Standard Breed Method Technique 86 

Complete for field work. 

Blank Pages 90 

For insertion of additional matter on bacterial 
control. 



COMPOSITE JARS 

Composite jars should be of approximately one pint capacity. 
Any one type of the following three may be used; all the jars, 
however, in a single factory should be uniform. 

1. Metal cap pint milk bottles. When these are vised care 
should be taken to see that the metal caps are not bent. Paper 
caps should always be used under the metal cap, to prevent 
evaporation of the watery part of the milk and thus result in a 
higher test than actual when the milk was delivered. 

2. Glass top pint preserv^e jars. The regulation rubber ring 
should always be used on this jar to check evaporation as pointed 
out under metal cap jars. 

3. Ground glass stoppered pint bottles. 

MARKING OF JARS 

All jars should be permanently marked with the dairy number 
to which they are assigned. Brass tags with the number stam.ped 
upon the face and attached to the bottle by wire are the most 
satisfactory means of identification. 

COMPOSITE JAR CABINET 

Composite Jars should be kept in a cabinet convenient to the 
weigh tank, this cabinet being provided with a door that can be 
locked. This cabinet should be locked except during the time when 
patrons' milk is being delivered, for the following reasons: 

1. Exposure to light has a tendency to harden butter fat. 

2. To guard against any from handling composite samples 
other than duly licensed tester. 

TAKING OF SAMPLES 

Each factory should be provided with a long-handled dipper 
of approximately one ounce capacity for the taking of the daily 
sample. Samples should be taken dkect from the weigh tank, 
one dipperful (1 oz.) constituting the daily sample from each 
dairy. Only in case of dairies delivering one can or less, may 

7 



sample be taken direct from can, provided the milk is thoroughly 
agitated with a stirrer. Stirring with composite sample dipper 
is not sufficient to thoroughly mix the milk. 

In factories not equipped with a weighing tank the sample 
should be taken in the following manner: 

Stir each can thoroughly. By means of a "milk sampler" 
(commonly called "milk thief") take a proportionate amount 
from each can by touching the bottom of the can with the "sam- 
pler." Transfer this to a metal cup of one pint size. Stir the 
milk in the cup and transfer a one ounce dipperful to composite 
jar. 

PRESERVATIVE 

During cold or moderate weather one No. 2 Corrosive Subli- 
mate tablet is sufficient to preserve the composite sample. In 
mid-summer two No. 2 tablets should be used. 

CARE OF COMPOSITE SAMPLES 

Great care must be taken in handling composite samples, 
in order to keep the milk in as near the condition of fresh milk 
as possible, and to prevent the butter fat from adhering to and 
drying on the sides of the jar. This is best accomplished by 
daily gentle whirling, giving the milk a rotary motion, at the same 
time keeping it as low in the jar as possible. It is advisable that 
this be done the first thing in the morning, before the patrons 
begin delivering, and when sufficient time is at hand to do this 
work properly. A jar should never be handled so that the milk 
or butter fat is spattered up on the sides or top of the jar. 

Carelessness in handling composite jars means extra labor 
on testing day and the possibility of an inaccurate result. 

TESTING DAYS 

Composite samples should be tested on the 7th, 14th, 21st, 
and last day of the month. These dates must be strictly adhered 
to. 

EQUIPMENT 

Bottles: The 8% milk bottle graduated at each .1% is the 
standard test bottle. 

Pipettes: Either the ordinary 17.6 c.c. pipette or the 17.6 
c.c. "Automatic" or " Up-to-Date " pipette may be used. The 
latter has the following advantages: 

8 



1. Insures a full 17.6 c.c. sample without manipulation of 
the fingers. 

2. Delivers a solid column of milk as all foam passes over 
to overflow bulb. 

Pipettes with broken tips should never be used. 

MARK OF CERTIFICATION 

All 8% test bottles and both plain and " Up-to-Date " pipettes 
should bear the "Mark of Certification of Accuracy" of the State 
Experiment Station of the state in which they are being used. 

WARMING COMPOSITE SAMPLES 

On testing day composite samples should be placed in a vat 
of warm water and brought to a temperature of approximately 
100 degrees F., by gentle shaking. 
Note: 

1. Excessive shaking may churn out butter fat. 

2. Temperature of sample should not exceed 100 degrees F. 
Above this temperature a part of the butter fat is converted to an 
oil which floats on the surface of the milk and is consequently lost 
in taking the pipette sample. 

LOOSING BUTTER FAT ADHERING TO JAR 

At this point the sample should be smooth with no signs of 
cream adhering to the sides of the jar. If an occasional jar shows 
cream adhering to the sides, this should be worked down into the 
milk by means of a soft wood stick or paddle. This is more 
satisfactory than the use of a brush and less dangerous in the 
possibilities it presents in carrying butter fat from one sample to 
another. 

PIPETTE SAMPLE 

When temperature of 100 degrees F. is attained the sample 
should be poured from one vessel to another several times to 
insure thoroughly mixing. The pipette sample of 17.6 c.c. is 
then taken, this being the equivalent of 18 grams of milk. In 
using the plain pipette the bottom of the meniscus shoiild be on a 
level with the 17.6 c.c. mark on the pipette, this mark being on a 
level with the eye. 

9 



COOLING THE SAMPLE TO 60 DEGREES F. 

The milk is then transferred from pipette to test bottle, the 
test bottle then being placed in water of about 58 degrees F., to 
cool the milk to approximately 60 degrees F. before the acid is 
added. Experience has shown that a 40 qt. can cover makes an 
ideal receptacle to cool and maintain a temperature of 60 degrees 
F. in the test bottles, the small hole on the side of the cover provid- 
ing an overflow for the cooling water, at just the right height as 
more bottles are added. A can cover will in this way accommo- 
date 12 bottles when arranged in a circle just inside the rim, 
thus two covers will accommodate 24 bottles for one run of the 
machine. Of course, the composite jars themselves ma}^ be cooled 
down to 60 degrees F., but this requires considerable time and 
much shaking of the jars which is undesirable, because continual 
shaking has a tendency to churn the butter fat in the sample. 
Also by the use of the can covers the measured sample can be held 
at exactly 60 degrees F. up to the moment the acid is added, even 
in very warm weather, which gives a decided advantage over the 
method of cooling the jars which always permits of the possibility 
of the measured sample rising in temperature before the acid is 
added. 

RINSING PIPETTE IN SAMPLE 

When measuring out a number of samples of milk in passing 
from one sample to another with the same pipette, the pipette 
should be rinsed by drawing it full of the milk to be sampled, this 
portion to be discarded. This eliminates the possibility of carry- 
ing butter fat from one sample to another and is more satisfactory 
than rinsing in water. 

ACID 

The sulphuric acid to be used in the test should be at a 
temperature of approximately 60 degrees F. Acid should be 
kept in glass stoppered bottles and not in open vessels, such 
as china pitchers, etc., or in metal top milk bottles as exposure 
to the air weakens it and leads to irregular results. The acid 
may be fairly dark colored and still be suitable for testing. It 
should, however, be free from particles as they have a tendency 
to come up in fat column of the completed test. 

10 



PURPOSE OF ACID 

The purpose of adding the acid is to destroy all the milk 
solids except the fat, which it does by moist combustion. In 
this process great heat is produced. This is advantageous since 
the fat must be kept in a liquid condition in order to perform 
the test properly. The neck of the test bottle gives percentage 
readings only when the fat is in a liquid condition. 

ADDING THE ACID 

In adding the sulphuric acid the bottle should be slanted 
and as the acid is poured in, the bottle should be revolved so 
that the acid will wash down any milk that adheres to the 
neck of the bottle. If this is not done, the milk dries on the neck 
of the bottle and is lost in the test ; it also causes a cloudy bottle 
neck and obscures the fat column when the test is completed. 
The acid and milk should be thoroughly mixed as soon as the 
acid is added to the bottle, else portions of the sample might be 
charred and so lock up small particles of fat. It is well to mix 
the bottle for at least half a minute after all the milk has appar- 
ently been dissolved by the acid. The mixing is done by holding 
the bottle by the neck between the thumb and the index finger, 
giving it a rotary motion from the wrist. If an up and down 
motion is used the contents of the bottle are likely to be spilled. 

COLOR FORMATION IN MIXTURE OF ACID AND MILK 

With -acid of the usual strength (1.820 to 1.830 specific 
gravity) and at a temperature of 60 degrees F. (milk in test 
bottles also at 60 degrees F.) 17.5 c.c. of acid should be used. 
This will provide just enough acid to slowly destroy the "milk- 
solids-not-fat" without too much heat and without charring 
them. In this reaction the characteristic color change is the 
best guide. As the milk and acid begin to mix the color of the 
solution becomes yellow at first, then passes through varying 
shades of yellow to violet, brown and finally dark brown. Too 
strong an acid or too high a temperature of either milk or acid 
produces a dense black color. The prompt formation of a 
black color will always give charred particles of milk solids in 
or under the fat column and this is a condition that leads to great 
inaccuracy in the test. Consequently, the color formation and 
the appearance of the fat column of the completed test (described 
later) are the best guides as to the amount of acid to be used. 

11 



HANDLING VERY STRONG ACID 

Occasionally a carboy of acid may be encountered, in the 
use of which even when the temperature of milk and acid is held 
down to 60 degrees F., still such an intense reaction may be 
brought about so as to char rather than dissolve the milk solids. 
The specific gravity of such acid is probably 1.835 or above, and 
it may be handled in one of the two following ways : 

1. By slightly reducing the amount of acid used. If black 
specks still appear in the fat column, resort to No. 2. 

2. By reducing the strength of the acid with water as 
follows: Pour into empty bottle 30 c.c. (about 1 oz.) of cold 
water. Add slowly one quart of the strong acid. Mixture will 
rise to a temperature of approximately 100 degrees F. This 
should be cooled to 60 degrees F. before using. Occasionally 
with exceptionall}^ strong acid it may be necessary to use 40 or 
50 c.c. of water. A little experimenting will soon determine 
the exact amount necessary. 

After the acid has been added and the solution of the milk 
solids is complete, the test bottle should be placed in the carrier 
cup of the machine so as to reduce the loss of heat to a minimum 
while the acid is being added to the other bottles. Just before 
centrifuging the bottles give each an extra shaking to insure 
complete solution. 

Note : Bottles should never be allowed to stand any length 
of time before centrifuging after the acid has been added. If 
at any time it is necessary to divide the work, the test bottles 
may be set away in a cool place after the 17.6 c.c. of sample has 
been placed in them and before the acid is added. When the 
acid is once added the test must be carried through to completion. 

CENTRIFUGING THE BOTTLES 

When less than 24 bottles are run at one time care must be 
taken to see that the machine is properly balanced. Centrifuge 
the bottles for five minutes at a speed of 1,000 revolutions per 
minute. Add hot water of a temperature of 150 degrees F. 
to the base of the neck of each bottle. Centrifuge for two 
minutes (and) again add hot water until the top of the fat column 
is a little below the 8% mark on the bottle. Centrifuge for one 
minute and begin taking readings immediately. 

12 



The above speed of 1,000 revolutions per minute applies 
to 12-inch diameter wheel (24 bottle) machine, this being the 
machine most commonly used. With the 18 -inch diameter 
wheel (36 bottle) machine the speed should be 800 revolutions 
per minute. 

TEMPERATURE OF BUTTER FAT 

In taking the readings remove the bottles one at a time from 
the machine, replacing the cover each time a bottle is removed 
so that an even temperature is maintained. The butter fat 
should be at a temperature of 135 to 140 degrees F. for at least 
three minutes before reading is taken, and this condition will 
be fulfilled if the above directions are carefully followed out. 
This condition can also be fulfilled by placing the bottles in water 
at a temperature of 140 degrees F., having the water deep 
enough to surround the entire fat column. 



READING THE FAT COLUMN 

The fat column should be read by 
means of sharp pointed dividers that 
permit of rapid adjustment and that 
will retain their position when once 
adjusted. The one point of the 
dividers should be placed opposite the 
base of the column, which is nearly a 
straight line when the testing is 
properly performed, the other point 
Read from °^ ^^^ dividers being placed oppo- 
A to B site the highest point at the top of 

the fat column. The lower point is 
then rapidly dropped to the zero 
mark, the result being opposite the 
upper point of the dividers. 

Emphasis is placed upon the fact 
that the highest point on the top 
of the column is the proper point 
to determine the upper limit. 
13 



REASON WHY FAT COLUMN IS READ AT EXTREME 
UPPER LIMIT 

The objections may be raised that we get too high results 
by reading from the extreme top points of the fat column just 
as if the upper surface was straight at these points instead of 
concave. While there is such an apparent error the excessive 
reading thus caused is only enough to make up for the loss of 
fat which cannot be separated from the rest of the liquid by 
centrifugal force and brought into the fat column. The amount 
of fat thus left in the mixture of milk serum and acid is ordinarily 
about .2% and this is about the amount of excess obtained by the 
approved method of reading the upper limit of the fat column. 

FAT COLUMN SHOULD BE WITHIN THE GRADUATED 
PORTION OF NECK 

If the lower limit of the fat column is below the zero mark 
or the upper limit above the 8% mark the reading should not 
be taken with dividers as the volume of the neck has only been 
determined between these points and we have no positive 
assurance that the remainder of the neck is of like volume. 
When the fat columns extend below the zero mark a little water 
may be added and the bottle centrifuged for an additional minute 
and then read, but when the column extends above the 8% 
mark the only resort is to repeat the test. 

CHECKING RESULTS 

After obtaining the readings and before the composite jars 
are put away to be held ten days as provided by law, the results 
just obtained shoiild be compared with the previous results on 
the same dairies and in those cases where the variation is greater 
than .2 of one per cent the test on these samples should be 
repeated to verify the results. 

RECORD OF RESULTS 

Neat and complete records of each testing date shotild be 
kept in special book provided for this purpose. This book 
should be available for inspection by the state or company 
officials at any time. 

14 



APPEARANCE OF COMPLETED TESTS 

Color of fat column should be straw yellow. If very dark 
it indicates too strong acid or too high a temperature of milk 
or acid. 

Black Specks 

Absence of foreign matter. Fat column should contain 
nothing but butter fat. If black specks or particles of charred 
casein are gathered at the lower limit or are incorporated in the 
body of the column it is an indication that the acid is too strong 
or that the temperature of milk or acid was too high, thus 
bringing about a too violent reaction which charred the milk 
instead of slowly dissolving it. 

Light Colored Specks 

If greyish white specks are present — and this is usually 
accompanied by a very pale yellow color and cloudy condition 
of the column itself — it indicates a weak acid or too low a tem- 
perature of milk or acid. In this instance the reaction between 
the acid and milk has not been sufficient to entirely dissolve the 
milk solids. 

Gas Bubbles 

If bubbles of gas appear as foam on top of the fat column 
they are generally due to the use of hard water containing lime. 
Usually this condition can be overcome by adding to the hot 
water tank a few drops of sulphuric acid. If this condition still 
persists it is advisable to collect sufficient rain water for use in 
testing. 

Too much importance cannot be placed upon the obtaining 
of a clear straw yellow colored fat column, absolutely free from 
all foreign matter. The presence of particles of any kind in or 
below the fat column indicates the inaccuracy of the results. 

CLEANING BABCOCK GLASSWARE 

Test bottles should be thoroughly washed between tests, 
and this should be done immediately on completing the test. 
If washing is delayed until fat has solidified it requires very much 
more labor to properly clean the bottles. When emptying 
bottles shake them vigorously as the contents run out. A 

15 



viscous sediment is formed by the action of the sulphuric acicf^ 
on the milk and the hot acid helps to loosen this sediment if 
the bottles are well shaken. Prepare a pail of hot soap solution 
and a pail of hot water. Four to six bottles may easily be 
taken in each hand and immersed in the soap solution until 
about one-half full. Repeat this operation twice, shaking 
vigorously while the bottles are emptying. Rinse twice in a 
like manner in the hot water. If bottles are then inverted so 
as to drain they will be thoroughly clean and bright. No brush 
is necessary unless the bottles have been allowed to stand 
some time before cleaning. 

The matter of keeping Babcock glassware absolutely 
clean at all times is not only one of personal pride on the part 
of the tester but it also insures more accurate results. 

LEGISLATION REGARDING TESTING 

In the spring of 1916, the legislature of New York State 
passed the Towner Act relative to taking composite samples in 
duplicate when requested by patrons. 

In 1917 further legislation regarding milk testing was passed 
in the form of an act making it necessary for any person testing 
milk or cream by the Babcock method where the result of such 
test is used as a basis for payment or for public record to hold 
a state license empowering him to perform such tests. 

On April 3, 1918, both of the above acts were amended so 
as to appear as one section of the Agricultural Law of the State 
of New York, to be known as Chap. 125, Section 35-a. In the 
amended law which is now in force provision was also made that 
composite samples must be resealed after test is completed and 
kept for at least ten days after making the test, for the purpose 
of permitting the Commissioner of Agricvilture or his duly 
authorized representative to examine and test same. 

The entire act in its present form follows: 

CHAPTER 125 
§ 35-a. Fat tests of composite samples of milk. Corpora- 
tions, associations or persons hereafter buying milk from 
producers of milk to be paid for on the basis of the percentage 
of milk fat contained therein and for that purpose taking samples 
therefrom to form a composite sample to be tested periodically 

16 



to determine its value on such basis, shall, at the request of the 
producer, take such samples in duplicate and subject them to 
the same treatment. At the end of the period for which the 
composite sample is being taken such corporation, association 
or person shall tender same to the producer thereof or to his 
authorized agent and give such producer, or his said authorized 
agent, the choice of one of the two composite samples so taken. 
Such producer is hereby permitted to send such duplicate 
composite sample so received to the head of the department 
of dairy industry of the college of agriculture at Cornell Uni- 
versity within ten days from the receipt thereof, properly 
marked for identification, and shall accompany same with his 
name and post office address. Such department head shall 
cause such sample to be tested for the per centum of milk fat and 
shall send a report of such test to the producer from whom it was 
received within ten days, or as soon thereafter as possible. 
Corporations, associations or persons hereafter testing samples 
of milk under the provisions of this section shall reseal the 
remaining portion of the composite sample from which the test 
was made, to determine the value of the milk bought from 
producers, and keep the same for at least ten days after the 
making of such test for the purpose of permitting the commis- 
sioner of agriculture or his duly authorized representative to 
examine and test the same. 

Any person testing milk or cream by the Babcock method 
where the result of such test is used as a basis for payment, or 
for official inspection, or for public record, shall first obtain from 
the commissioner of agriciilture a license to do such testing. 
Such license shall be granted upon satisfactory evidence of good 
moral character and the ability to make such tests based upon 
satisfactorily passing an examination set by the commissioner 
of agriculture. Such examination shall be based upon methods 
for making the Babcock test as outlined by the New York 
state college of agriculture and the commissioner of agriculture. 
Licenses granted under this section shall be revocable by the 
commissioner of agriculture upon evidence of dishonesty, in- 
competency or inaccuracy. Licenses shall be granted for one 
year renewable at the discretion of the commissioner of agricul- 
ture without further examination. 

§ 2. This act shall take effect immediately. 

17 



TESTING FROZEN MILK 

Partly frozen milk should never be sampled for testing 
since a sample of such milk will not be representative. Such 
milk should be melted and carefully remixed before any is re- 
moved for testing, but in melting the ice a temperature of not 
over 85 degrees F. should be used. Too high a temperature is 
likely to cause a separation of the fat in the form of an oil, and 
when the fat thus separates it is impossible to remix it evenly 
with the milk. 

TESTING SOUR MILK 

Sour milk should not be tested unless such testing 
is absolutely necessary. Composite samples will not turn sour 
if sufficient preservative is used and if the jars are thoroughly 
washed and the samples well cared for during the composite 
period. It is difficult to test sour milk because the casein has 
been precipitated and the fat is locked u]) in the particles of curd, 
making an even distribution of the fat impossible. The consist- 
ency of sour milk can be made more like that of normal milk by 
the addition of a strong alkali which drives or tends to drive the 
casein into suspension. The particles of fat are then released. 
Caustic soda and caustic potash are useful in restoring the 
consistency of sour milk and it is best to add them in the dry 
form. 

TESTING CHURNED MILK 

Churned milk should not be tested if it can be avoided. 
When it is absolutely necessary to test churned milk the milk 
should be heated to about 85 degrees F. and well shaken, and 
the pipette sample drawn quickly, 

CONCLUSIONS 

Carefulness and attention to details result in accuracy in 
Babcock test work. 

The following very important features will bear repetition: 

1. The daily samples should be taken in such a manner, 
and the composite sample in the jar should be so handled during 
the entire period, that on testing day when the 17.6 c.c. of milk 

18 



be transferred to the test bottle it will be an exact representa- 
tion of the entire bulk of milk delivered during the entire period, 
by each individual patron. 

2. The test should be so conducted that on completion it 
will give a clear fat column of straw yellow color with no evidence 
of either light or dark particles in or under the column. 

3. An accurate reading should be made by means of sharp 
pointed dividers in which the extreme limits of the column 
are included. 



19 



CREAM 

The Babcock test can be used in ascertaining the amount 
of fat in cream but certain precautions and modifications are 
necessary to insure correct results. 

The four main factors to be considered are: 

1. Taking the sample. 

2. Getting the correct amount of cream into the test 
bottle. 

3. Conducting the test so as to obtain a clear fat column 
absolutely free from foreign matter. 

4. Reading the fat column correctly. 

SAMPLING CREAM 

The importance of thorough mixing of the cream in its 
original container is essentially important. If the sample is 
taken from a can the cream should be thoroughly mixed by 
stirring for at least a half minute. After thorough agitation 
it is necessary to take up but a very small sample (about 2 oz. 
being sufficient for one test and a duplicate). The taking of 
larger samples merely means a waste of cream. 

WEIGHING THE CREAM 

The sample should be warmed to a temperature of 85 to 100 
degrees F., and it should then be poured several times from one 
bottle to another, care being taken to see that the sample is 
thoroughly smooth. Merely stirring a sample with a pipette 
or blowing air through it by means of a pipette is very poor 
practice and gives only indifferent mixing. The matter of 
thoroughly mixing samples by warming to 85 degrees F. and 
pouring several times back and forth is especially important 
after the samples have stood awhile at room temperatures before 
testing. 

If small lumps are present the cream should be strained 
through a small sieve, at the same time working out the lumps 
so as to make the cream absolutely smooth before sample is 
weighed. 

Cream should never be measured but should always be 
weighed for the following reasons: 

20 



1. More fat adheres to the inside of the pipette than in the 
case of milk. 

2. The weight of cream decreases as the per cent of fat in 
cream increases, since the butter fat is lighter than the other 
constituents in cream. 

3. Separator cream is more or less filled with bubbles of 
air and ripened cream contains gases produced by fermentation. 
These decrease the weight of a given volume of cream. 

CREAM TEST BOTTLES 

The 9 gram 50% bottle and the 18 gram 50% bottle are the 
standard bottles for testing cream. The 9 gram 50% bottle is 
considered the Borden standard. This bottle is more economical 
in the amount of cream it requires for a test, and since it is 
graduated in 0.5% it gives an accurate reading. 

The old style 18 gram 15, 25 and 30% bottles should be 
discarded. With the latter bottles it would be necessary to 
weigh out an aliquot part of 18 grams (viz., 9 grams or 6 grams), 
the result then being multiplied by two or three as the case may 
be. The main objection to this method is that if a slight error 
be made in the test, it will be two or three times as great in the 
final result, because the reading must be multiplied by that 
factor representing the aliquot part of 18 grams used. 

CONDUCTING THE CREAM TEST 

The actual test on the weighed sample may be conducted 
in either of the following ways: 

1. Babcock Test. To the weighed sample (9 grams of 
cream) 9 c.c. of water are added. This is to retard the action 
of the acid, and in this way a burned fat column may be avoided. 
The water should be warm enough to rinse into the body of the 
bottle all the cream that adheres to the neck. 

Add 16 to 17.5 c.c. of sulphuric acid, specific gravity 1.82 to 
1.83, at 60 degrees F. until mixture immediately after shaking 
resembles coffee with cream in it. Whirl in Babcock machine 
at proper speed five, two and one minutes respectively, filling 
the bottles with hot water (temperature 150 degrees F.) to the 
bottom of the neck after the first whirling, and to near the top 
of the graduation after the second whirling. Result as later 
described under "Flattening of Meniscus." 

21 



2. Modified Lefifman and Beam Test or Amyl Alcohol 
Method. To the weighed sample of cream (9 grams) in the test 
bottle \'}/2 c.c. of a mixture of amyl alcohol and hydrochloric are 
added and thoroughly mixed by giving the bottle a rotary 
motion. (The mixture of amyl alcohol and hydrochloric acid 
consists of equal parts of each of these chemicals. This should 
be prepared in advance.) A}/2 to 5 c.c. of sulphuric acid are then 
added, pouring a little of the acid at a time, meanwhile giving 
the bottle a rotary motion. After the acid has been added allow 
the bottle to stand about two minutes or until the mixture turns 
dark and the butter fat has risen to the top in a clear layer. 
Fill the bottle to the 50% mark with a hot and freshly made 
mixture of equal parts of water and sulphuric acid. (Caution — • 
Always add the acid to the water.) 

Centrifuge the bottle at 1,000 revolutions per minute for 
five minutes. Only one whirling is necessary. 

The Babcock method is considered by the New York State 
Department of Agriculture the official method of testing both 
milk and cream. Our experience has been that the Amyl 
Alcohol method is very useful in testing cream as it is very easily 
performed and gives a clear butter fat column that is easily read. 

TEMPERATURE OF FAT COLUMN 

The fat column should be at a temperature of 135 to 140 
degrees F. when read. In order to have the fat column at this 
temperature, the bottles should be immersed in a water bath 
at a temperature of 140 degrees F. for at least three minutes 
before reading the result, the water in the bath being deep 
enough to completely immerse the entire fat column. This 
adjustment of temperature of fat column is advisable in both 
Babcock and amyl alcohol methods. 



22 



FLATTENING THE MENISCUS 

In order to obtain an accurate result when reading the fat 
column of the cream test, it is necessary to flatten the meniscus 
or curved upper end of the column so that a straight line may be 
obtained at this point. This is 
equally applicable in both Bab- 
cock and amyl alcohol methods. 
In this respect the reading of the 
cream test differs from that of 
whole milk. In the latter case 
the extreme limits of the column 
are included to make up for the 
residual amount of fat in the base 
of the bottle as pointed out in 
the manual under milk testing. 

In order to accomplish this 
desired flattening of the menis- 
cus a few drops of colored mineral 
oil or colored "Glymol" are 
added after the test bottle is 
taken from the water bath. The 
mineral oil should be added with 
a medicine dropper allowing the 
liquid to run down the inside of 
the neck of the test bottle until 
it reaches the fat column over 
which it will then spread giving 
a sharp line of demarcation. It 
should not be dropped directly 
into the fat for then it will mix 
with the fat and give a ragged 
line. 

The reading should be made 
from the lower limit of the 
column to the sharp line of 
demarcation between the butter 
fat and mineral oil, as shown in 
t)pposite cut. 




METHOD OF READING THE 
PERCENTAGE OF FAT IN 
CREAM 

The arrows indicate the points 
on the scale at the ends of the 
fat column at which the readings 
should be taken. 



23 



TESTING SKIMMED MILK 

vSkimmed milk should be tested by the ordinary Babcock 
test. The regulation skimmed milk bottle should be used, this 
bottle having two necks, one having a very small bore in order 
to measure the small amount of butter fat accurately, the other 
being a funnel tube for conveniently adding the measured sample 
of 17.6 c.c. and the proper quota of acid. The Troy-Wagner 
bottle is well adapted for this test, this bottle having a small 
hole in the funnel tube to allow the escape of air when milk and 
acid are mixed and thus prevent the mixture of milk and acid 
being forced up into the graduated neck, and also to permit the 
more thorough washing of the fat when the water is added. 

In the skimmed milk test 18 or 19 c.c. of acid should be used, 
the acid being added in two approximately equal portions with 
an intermediate shaking. 

Skimmed milk bottles should be placed in the machine with 
the funnel tube to the outside. 

The globules of fat in skimmed milk are very small and for 
this reason it is very difficult to bring them to the surface by 
centrifugal force. The bottles should therefore be whirled for 
periods of ten minutes, two minutes, and one minute, the hot 
water being added between these periods as in the case of whole 
milk. 

Efficiently operated separators should never turn out a 
skimmed milk of more than .02 of 1% butter fat. 



24 



BUTTER 

Preparation of Sample 

A mass of butter is so variable in its composition, owing to 
the uneven distribution of water, that it is difficult to obtain a 
representative sample unless great care is exercised. A sample 
for testing should therefore be made up of parts selected from 
different places in the churn or package. The sample thus 
selected should be placed in a fruit jar or composite sample 
bottle and heated with constant agitation in water of about 
1 10 degrees F., until the butter is of consistency of heavy cream. 
The sample should then be cooled, shaking the jar constantly 
to keep the moisture evenly distributed. 

TESTING FOR BUTTER FAT 

Weigh 3 grams of sample as prepared above into a 9 gram 
cream test bottle. Either the Babcock or Amyl Alcohol method 
(as described under cream testing) may be used. In using the 
Babcock method about 8 c.c. of sulphuric acid should be used, 
and in the amyl alcohol method 4 c.c. of sulphuric acid are 
sufficient. The reading should be multiplied by three to obtain 
the final result. Mineral oil should be used to flatten the 
meniscus. 

TESTING FOR MOISTURE 

In the testing of butter for moisture special equipment is 
required. Among a number of tests on the market, our experi- 
ence has been that the test known as the "Ames-Cherry" test 
gives very satisfactory results and is also very easily operated. 

The equipment for this test consists of a tripod supporting a 
paraffine heating bath in which is inserted two aluminum cups 
so constructed that one cup fits tightly within the other. An 
alcohol lamp for heating the paraffine bath and an accurate 
thermometer complete the outfit. Direction for conducting 
this test follow: 

1st. Start the paraffine to heating, using alcohol lamp that 
is furnished with the outfit, filling the copper container about 
one third full of paraffine. 

25 



2d. Place butter in an open container or vessel in which 
butter can be stirred and set in water at about 100 degrees F. 
until butter is soft and then stir until you have a thorough 
emulsion. 

3d. Weigh out the 10 gram sample of butter into the inner 
or smaller aluminum cup. 







^zrZ2:> ^ 



ti,___ ^ 



1f 



^' 



4th. Set cup containing sample inside the larger aluminum 
cup and fit the outer aluminum cup into the copper paraffine 
kettle, pressing down so that the flange on the paraffine kettle 
will hold the outer aluminum cup in place. The time required 
to expel moisture will be from 5 to 7 minutes, depending on 
amount of moisture in butter. For testing creamery butter an 
even temperature of 175 degrees Centigrade is required. If you 
heat as high as 180 Centigrade you are liable to burn the sample. 

5th. The cup and contents should be allowed to cool 
before weighing it back, as it is enough lighter when hot to make 
2% to 4% difference in moisture reading. 

In the copper paraffine kettle flange there is a small hole or 
opening into which special Centigrade thermometer is inserted. 
The end of the thermometer should be lowered to within about 
}/2 inch of the bottom of the kettle by adjusting the wire clamp 
that is furnished with the thermometer. 

By following the above directions carefully and heating the 
sample from 5 to 7 minutes, there is no danger of burning. The 
difference in weight before and after heating, that is, the loss in 
weight, divided by the original weight of the butter, and this 
result multiplied by 100, gives the percent of moisture. 

26 



For example: 

Original weight of butter 10.00 grams 

Weight after heating 8.54 " 

Loss in weight 1.46 " 

1.46 X 100 

= 14.6% moisture 

10 
If a special butter moisture scale is used, the percent of 
moisture is given direct on the graduated beam of the scale, 
and the above calculation is then unnecessary. 

COMPUTING OVERRUN IN BUTTER 

Overrun is the increase in the amount of butter made from 
a given amount of fat, or it is the sum of the moisture, the salt, 
and the casein of the butter, minus the losses in manufacture. 
For example: 

Butter maker X has 1,000 pounds of cream testing 35% fat. 

From it he makes 400 pounds of butter. Compute the percentage 

of overrun and the value of the overrun at 50 cents per pound. 

1,000 X .35 = 350, number of lbs. fat. 

400 (lbs. butter)— 350 (lbs. fat) = 50, weight in lbs. 

of overrun. 
50 -- 350 = .142. 

.142 X 100 = 14.2% overrun. (Answer.) 
$.50 X 50 = $25.00, value of overrun. (Answer.) 

Another example: 

Butter maker Y is more careful in preventing leaks and 
wastes, and he understands butter making better than does X. 
From 1,000 lbs. of cream testing 35% fat he makes 420 lbs. of 
butter. Compute the percentages of overrun and its value at 
50 cents per lb. 

1,000 X .35 = 350, number of lbs. fat. 

420 (lbs. butter)— 350 (lbs. fat) = 70, weight in lbs. 

of overrun. 
70 -f- 350 = .20. 
. .20 X 100 = 20%, overrun. (Answer.) 

$.50 X 70 = $35.00, value of overrun. (Answer.) 
Butter maker Y has made from the same amount of fat $10 
worth more butter than has X. 

27 



BUTTER FAT TEST ON BUTTER MILK 

Tests for butter fat should be made on the buttermilk re- 
maining to determine the completeness of the churning. This 
test may be performed as outlined under skim milk. When 
butter fat present in buttermilk is excessive, the 8% whole milk 
bottle should be used instead of the usual skim milk bottle. 



COMPUTING LOSS OF BUTTER FAT IN CHURNING 

In determining the approximate amount of buttermilk, sub- 
tract the weight of the butter — not the fat alone — ^from the weight 
of the cream. 

For example, if 1,000 lbs. of cream were used for churning, 
and 400 lbs. of butter were made, the amount of buttermilk 
would be 1,000 — 400 = 600 lbs. If the buttermilk had a butter 
fat content of .5%, then: 

600 X .005 =3.0 lbs. butter fat. 

3.0 X 1.20 = 3.6 lbs. butter (overrun.) 

.50 X 3.6 = $1.80 value of butter fat lost in buttermilk. 



28 



CHEESE 

In the sampling of cheese similar precautions must be used 
in order to obtain a representative sample as discussed in the 
sampling of butter. The most satisfactory method of obtaining 
a representative sample is to draw three plugs from the whole 
cheese, viz: one from center, one about one inch from the outer 
edge and one half way between these two. If only one plug 
can be drawn this should be taken at a point half way between 
the center and the margin. The plugs should be taken perpendi- 
cular to the end surface of the cheese and should reach either 
entirely through the cheese or just half way. The plugs should 
be carefully cut into small pieces and the sample for test bottle 
should be weighed promptly to prevent loss of moisture. 



TESTING CHEESE FOR BUTTER FAT 

As the normal amount of fat in American cheddar cheese 
will run from 33 to 38%, it is best to use the 9 gram 50% bottle 
in making the fat determination. Weigh 4.5 grams of the 
sample, prepared as above described, into the 9 gram 50% 
bottle. Then add 15 c.c. of hot water to the weighed sample and 
agitate until the water disintegrates the cheese. This may be 
hastened by adding a few drops of acid and keeping the bottle 
in slightly warm water until no more lumps are seen in the liquid. 

The test may be run by either the original Babcock method 
or the amyl alcohol method, in either case using a little more 
sulphuric acid than usual to completely dissolve the high per- 
centage of solids — not — ^fat present in the cheese. Before 
reading the result mineral oil should be added to flatten the 
meniscus. Multiply the reading by two to obtain the final 
result. 

TESTING CHEESE FOR MOISTURE 

In testing cheese for moisture, the Ames-Cherry apparatus 
(described under testing butter for moisture) with slight modi- 
fications, may be used. These modifications consist in using a 
special glass flask instead of the inner aluminum cup of the 
Ames-Cherry apparatus, and a small cover for the outer cup, 
with a hole in it through which the neck of the flask may pass. 

29 



The directions for this test, which was originated by Prof. 
H. C. Troy of the New York State College of Agriculture, follow: 

In operating the test, the alcohol lamp is first lighted, so 
that the parafin bath may be warming while the test sample is 
under preparation, A representative sample of the cheese, which 
may be taken with a cheese trier and held in a glass-stoppered 
sample jar, is then cut into particles about the size of kernels of 
wheat without removing it from the jar. This may be done 



with an ordinary table knife that has had the end squared and 
sharpened. The clean dry flask is then accurately balanced 
on the scales and a 5 -gram weight is placed in the opposite scale 
pan. Particles of cheese from the prepared sample are put into 
the flask until the scales comes to an exact balance. Great care 
should be taken to avoid loss of moisture from the cheese during 
the preparation of the sample. 

With the thermometer in the parafin bath registering a temper- 
ature between 140 degrees and 145 degrees C. (or between 284 

30 



degrees and 293 degrees F.), the flask is placed in the cup of the 
parafin bath and the flat, disk-shaped cover is adjusted over the 
apparatus. The flask should remain in the bath for fifty minutes 
the temperature being kept between 140 degrees and 145 degrees 
C. all the time. The flask is then removed, covered, and al- 




lowed to cool to room temperature in a dry place. It is then 
weighed, and the quotient obtained by dividing the loss in 
weight by the original weight, multiplied by 100, gives the 
percentage of water in the cheese. The following shows the 
method of computation. 

31 



Problem. Five grams of cheese was heated until the water 
contained in it was evaporated. The remaining substance 
weighed 3.15 grams. What percentage of water did the cheese 
contain? 

Answer : 

5.00—3.15 = 1.85 

1.85 4- 5 =-0.37 

0.37 X 100 = 37 (percentage of water in cheese) 

A butter moisture scales with an extra 5 -gram weight may 
be used for weighing out the 5 grams of cheese. If the scales 
indicates the amount of moisture in 10 grams of butter by per- 
centage graduations on its beam or by percentage weights, then 
it will be necessary to multiply by two the percentage indicated 
by such scales when only 5 grams of cheese is used. 

Caution : 

In operating either the cheese or butter moisture tests, the 
temperature of the parafin bath should be carefully watched, 
so as not to over heat it. If over heated it may take fire. If a 
bath should ever take fire, smother out the flame. Do not throw 
water on it, since water would spread and intensify the flame. 
If the indicated temperatures are not greatly exceeded, there is 
no danger of fire. 

CHEESE YIELD 

In computing the cheese yield of milk, using the fat content 
as a basis of calculation, the results of careful experiments 
conducted by state experiment stations, show that within reason- 
able limits, the yield of cheese increases with the percentage of 
fat in the milk. 



Percentage of 


Lbs. 


of Cheese from 


Lbs 


. of Cheese for 


fat in milk 


100 lbs. of milk 


lb. 


of butter fat in 










milk 


3.0 




8.28 




2.76 


3.5 




9.41 




2.68 


4.0 




10.56 




2.64 


4.8 




12.51 
32 




2.60 



Actual Cheese Yield 

In order to obtain the actual yield of cheese, divide the 
number of pounds of cheese made by the number of pounds of 
milk used. Multiply the result by 100 to get the yield of cheese 
per 100 pounds of milk. For example, if 480 pounds of cheese 
are obtained from 5,180 pounds of milk, what is the yield? 

480 ^ 5,180 = .0927 

.0927 X 100 = 9.27 lbs. cheese per 100 lbs. milk 

Yield per pound butter fat 

To obtain the yield of cheese per pound butter fat, samples 
should be taken of the thoroughly mixed milk, and tested by 
the Babcock method. For example, using the same batch of 
cheese given above (under "Actual Cheese Yield"), let us 
assume that the butter fat test on the whole milk was 3.5. Then : 

5,180 X .035 =- 180.30 lbs. butter fat 
480 (lbs. cheese) -^ 180.30 = 2.66 lbs. cheese per lb. 
butter fat 



33 



TESTING PLAIN CONDENSED OR EVAPORATED MILK 

Weigh carefully 9 grams of well mixed plain condensed milk 
into a 10% (old style) milk test bottle. The 10% bottle is speci- 
fied because of its larger neck, which permits the weighing of plain 
condensed milk more readily than the present 8% milk bottle. 
Add 9 c.c. of water. Mix condensed milk and water thoroughly. 
Add 3 c.c. of a mixture made from equal parts of hydrochloric 
acid and amyl alcohol. Again mix thoroughly. Add slowly 
and a little at a time 12 to 14 c.c. sulphuric acid. Allow to 
stand until fat has risen to surface and mixture has turned dark. 
Fill to just below 10% mark with a hot and freshly made mixture 
of half sulphuric acid and half water. Whirl for 5 minutes in 
Babcock tester. Add colored mineral oil to flatten meniscus. 
Read with dividers. Multiply reading by two for final result. 



34 



ACIDITY TEST 

To determine the percent of acidity in either milk or cream, 
special apparatus is required. All acidity tests are based upon 
the principle of neutralizing the acid present in a definite volume 
of milk by a solution containing a known amount of alkali, the . 
common alkali solution being what is commonly known among 
chemists as a deci-normal (y^) sodium hydrate solution. An 
indicator called " phenolphthalein " is also used. This indicator 
gives a pink color in the presence of alkali, and is colorless in the 
presence of acid. 

The following apparatus is necessary for performing the 
acidity test: 

1 — 25 c.c. burette graduated at each y^^ c.c. 
1 — burette stand 
1 — white cup or casserole 
1 — stirring rod 
1 — 17.6 c.c. milk pipette 
^ — sodium hydrate (alkali) solution 

Indicator (phemolphthalein) . 

Performing of Test 

Measure 17.6 c.c. of milk into the white cup. Rinse the 
pipette by drawing clean water to the 17.6 c.c. mark, and add 
this rinse water to the cup. Then add 4 or 5 drops of the indi- 
cator to the mixture of milk and water. 

Fill the burette with the ^ alkali solution. Draw off the 
y^ alkali into another vessel, through the stop cock of the 
burette until the solution stands at exactly the zero mark on the 
burette. 

Now place the cup containing the milk to be tested under 
the stop-cock of the burette, and add the y^ alkali solution 
very slowly, meanwhile stirring the milk thoroughly with the 
stirring rod. When the mixture assumes a very light permanent 
pink color, stop adding the alkali solution. At this part of the 
test, the alkali shoiild be added drop by drop. 

Calculating the Result 

Read from the burette the number of c.c. of alkali required 
to produce the light permanent pink color. Divide this number 

35 



by two and the answer will represent the percent of acidity of 
the milk in terms of one-hundred ths percent. 

For example, if it required 2.8 c.c. of alkali, then 28 divided 
by 2 equals 14, or .14% acidity. 

Standards for Milk 

Fresh milk will give acidity tests between the lirhits of 
.12% to .15%. If the acidity is higher than .18%, it indicates 
that lactic acid fermentation has been going on, and that the 
milk can no longer be considered fresh. 

Precautions 

Precautions to be observed in running the acidity test: 

1. All apparatus used in running this test must be abso- 
lutely clean, and it must be kept apart from other testing glass- 
ware. A small trace of sulphuric acid will affect the test very 
markedly, making the result unreliable. 

2. Alkali solution should never remain in the burette after 
the test is completed. It should be immediately drawn back 
in the alkali bottle. 

3. Alkali bottle should be tightly stoppered at all times. 
This solution loses its strength rapidly when exposed to the air. 
When weakened, it gives results that indicate too high acidity 
in the milk. 

4. No more alkali should be added when a light permanent 
pink color is obtained. Do not add alkali until the deep pink 
color is obtained. This will give too high acidity. 

5. Finally, it shotild be borne in mind that the acidity test 
is a very delicate one, and that the resiilts obtained are very apt 
to be worthless if the test is not properly performed, or if the 
alkali solution is not properly protected from the air. 



36 



LACTOMETER 

Lactometer readings are regularly obtained in the Eastern 
and Middle States by means of the New York Board of Health 
Lactometer. 

In using the Lactometer the following procedure is recom- 
mended: Fill the cylinder with the carefully mixed milk at a 
temperature of 50 to 70 degrees F. Insert the lactometer 
and note the point at which it comes to equilibrium on the scale 
at the surface of the milk. The lactometer is graduated on the 
basis that all examinations are to be made at 60 degrees F. 
It is therefore necessary to take the temperature of the milk 
and to correct the reading by adding three tenths of a point 
for each degree of temperature above 60 degrees F., or to subtract 
.3 point for each degree below 60 degrees F. This rule holds 
good only when the range of temperature is within the limits 
of 50 degrees F. and 70 degrees F. 

The best practice is to bring the sample to a temperature 
of exactly 60 degrees, F, and then take the lactometer reading. 



PRECAUTIONS IN USING LACTOMETER 

The following precautions should be observed in obtaining 
lactometer readings : 

1. Milk should not be examined until about one to two 
hours after milking as the lactometer reading is lower for a while 
after being drawn than it is later, due to the presence of gases 
in the freshly drawn milk. 

2. The sample must be thoroughly mixed. 

3. The lactometer must be kept clean. 

4. The lactometer cylinder must be large enough to allow 
the instrument to float freely without the possibility of friction 
between the lactometer and sides of cylinder. 

5. Composite samples containing preservatives always 
give a higher reading than fresh milk. Accurate lactometer 
determinations can only be obtained from fresh milk. 

37 



QUEVENE LACTOMETER 

In some dairy sections the Quevene lactometer is used in 
place of the N. Y. Board of Health lactometer. The readings 
on the Quevene scale differ from those on the Board of Health 
scale; for example, a reading of 29 on the Quevene is equivalent 
to 100 on the B. of H. 

To convert Quevene reading to the equivalent B. of H. 
reading : 

Divide the Quevene reading by .29. 

Example: What is the equivalent B. of H. reading of 

30.5 Quevene? 
Answer: 30.5 divided by .29 equals 105.2 B. of H. 
To convert B, of H. reading to Quevene reading: 
Multiply the B. of H. reading by .29. 
Example: What is the equivalent Quevene reading of 

108 B. of H.? 
Answer: 108 X .29 equals 31.32 Quevene. 

CALCULATION OF TOTAL SOLIDS 

When the butter fat content and the B. of H. lactometer 
reading of a sample of milk are known, the total solids may be 
readily calculated by the following formula: 

L X .29 

X 1.2 F = T. S. 

4 
L representing the B. of H. lactometer reading, F the 

butter fat content, and T. S. the total solids. 
Example: What are the total solids in sample of milk 
having 3.6% butter fat and 108 B. of H. lacto- 
meter reading at 60 degrees F.? 
Answer: 108 X .29 

X (1.2 X 3.6) = T. S. 

4 

or 
31.32 
X 4.32 — T. S. 



4 
or 

7.83 X 4.32 = 12.15 Total Solids. 
38 



TESTING EQUIPMENT 

A stock of carefully selected and accurate glassware and 
supplies for testing milk and its products is maintained at the 
laboratory headquarters of our Company to meet the require- 
ments of our country branches. When a factory wishes testing 
material a requisition should be made on Purchasing Department 
(Form No. 0-1). The Purchasing Department will then 
authorize the laboratory to make shipment. All orders for 
testing supplies should be sent to the Purchasing Department 
and not to the laboratory. 

While it is the aim of the Company to promptly supply all 
necessary equipment it should be borne in mind that these articles 
are costly and they should be handled carefully in order to keep 
breakage down to a minimum; and each factory should order 
supplies only in accordance with its actual requirements. 

The articles that are regularly carried in stock follow: 

Acidometer (for determing specific gravity of acid) 

" jars 

Acid measures (17.5 c.c.) 
Acid-alcohol mixture for cream test 
Bottles — 6 inch milk test bottles (8%) 
" " cream test bottles (50%) 

" " skim milk test bottles 

" glass stoppered (1,000 c.c.) for acid 

Corrosive sublimate tablets (No. 2) 
Cylinders — -graduated (10 c.c.) for cream test 

" " ( 8 oz.) for handling acid 

Dividers — for reading butter fat columns 
Lactometers (N. Y. Board of Health scale) 
Lactometer jars 
Milk Samplers 
Pipettes— Milk (17.6 c.c.) 

" to be used when weighing cream (9 c.c.) 

Thermometers — floating dairy 
" platform. 



39 



STANDARDIZING 

Standardizing milk or cream consists in raising or lowering 
the fat content to a fixed standard. This is done by adding to 
the material to be standardized, milk or cream of a higher or 
lower percentage of fat. Naturally the quantities of material 
of two different butter fat contents that should be mixed in order 
to obtain the desired result, is the first problem that presents 
itself. 

The original method of computing problems in standardiza- 
tion is long and difficult, but a method suggested by Prof. R. A. 
Pearson of Cornell University is comparatively simple and is 
herewith described: 

Draw a rectangle and write in the center the desired test. 
Write opposite the upper and lower left hand corners the tests 
of the materials you have on hand. 

Determine the difference between figure in the upper left 
hand corner and that in the center, and write this result in the 
lower right corner — that is, subtract diagonally. Now determine 
the difference diagonally between the figure in the lower left 
hand corner and that in the center, and write the result in the 
upper right hand corner. 

For example: If you have 3% milk and 25% cream, and 
wish to make 20% cream: 




>22 



That is, 5 parts of 3% milk, when mixed with 17 parts of 
25% cream, will give 22 parts of 20% cream. 

If the number of quarts of each of the two to be mixed, per 
40 quart can, is desired, the following calculation may be used: 
%2 X 40 = 9.08 qts. of 3% milk. 
^%2 X 40 = 30.92 qts. of 25% cream. 
40 



Another problem that often presents itself is when we have 
a definite amount of cream of a high test and we wish to know 
how many quarts it will make of a certain lower test, and how 
much milk should be added to make the proper mixture. 

For example: if we have ten cans (400 quarts) of 34% 
cream, and we wish to know how many cans of 20% cream can 
be made, by adding 3.6% milk to it: 



400 QT5.34% 



3.67o 



16.4 




14 



This shows that for every 16.4 quarts of 34% cream, 14 
quarts of 3.6% milk should be used; so divide the 400 qts. by 
16.4, and multiply this figure by 14, which gives 341.4 quarts of 
3.6% milk to use. By adding 400 qts. to 341.4 qts., we will get 
741.4 qts. of 20% cream; or, 

^ X 14 = 341.4 qts. of 3.6% milk. 
400 + 341.4 = 741.4 qts. of 20% cream. 

The usual grades of cream marketed by our Company are 
the 20% butter fat, or ''Route Cream," and the 38% and 40% 
butter fat, or "Extra Heavy Cream." Cream as it comes from 
the separators will very seldom meet with these requirements 
as to butter fat content. Accordingly it becomes necessary to 
standardize it by adding the proper amount of whole milk. 
In-order to assist the cream operator, tables are herewith given, 
covering the possible range of separator creams, in which are set 
forth the number of quarts of cream and the number of quarts 
of milk (testing 3.6%) which, when mixed, will give 40 quarts 
of cream of the desired test. Milk testing 3.6% is a fair average 
that will apply to all plants. 



These tables are given on the following pages : 

41 



TABLE NO. 1 
To Make 20% Cream 



When 


To make 40 qts., use 


cream tests 


qts. cream 


qts. milk 


21% 


37.7 


2.3 


22% 


35.6 


4.4 


23% 


33.8 


6.2 


24% 


32.2 


7.8 


25% 


30.7 


9.3 


26% 


29.3 


10.7 


27% 


28.0 


12.0 


28% 


26.9 


13.1 


29% 


25.8 


14.2 


30% 


24.8 


15.2 


31% 


23.9 


16.1 


32% 


23.1 


16.9 


33% 


22.3 


17.7 


34% 


21.6 


18.4 


35% 


20.9 


19.1 


36% 


20.2 


19.8 


37% 


19.6 


20.4 


38% 


19.1 


20.9 


39% 


18.5 


21.5 


40% 


18.0 


22.0 


41% 


17.5 


22.5 


42% 


17.1 


22.9 


43% 


16.6 


23.4 


44% 


16.2 


23.8 


45% 


15.8 


24.2 



42 



TABLE NO. 2 
To Make 38% Cream 



When 
cream tests 


To make 40 qts., use 


qts. cream 


qts. milk 


39% 


38.9 


1.1 


40% 


37.8 


2.2 


41% 


36.8 


3.2 


42% 


35.8 


4.2 


43% 


34.9 


5.1 


44% 


34.1 


5.9 


45% 


33.2 


6.8 


46% 


32.4 


7.6 


47% 


31.7 


8.3 


48% 


31.0 


9.0 


49% 


30.3 


9.7 


50% 


29.7 


10.3 



43 



TABLE NO. 3 
To Make 40% Cream 



When 


To make 40 qts., use 


cream tests 




, 




qts. cream 


qts. milk 


41% 


39.0 


1.0 


42% 


37.9 


2.1 


43% 


37.0 


3.0 


44% 


36.0 


4.0 


45% 


35.1 


4.9 


46% 


34.3 


5.7 


47% 


33.5 


6.5 


48% 


32.8 


7.2 


49% 


32.0 


8.0 


50% 


31.4 


8.6 



44 



Before standardizing operations are attempted, an accurate 
test must be obtained on the cream that is to be used. This 
can be best obtained by thoroughly mixing the cream on hand 
in a vat pasteurizer, or in a regulation cream vat. Samples 
should then be taken and run in duplicate by the Babcock or 
Amyl Alcohol method. Let us assume that these tests show- 
that the butter fat content is 48%, and that twenty (20) cans of 
cream testing 38% are desired. 

By consulting Table No. 2, we find that when 48% cream is 
reduced to 38% that 31 qts. of this cream and 9 qts. of milk will 
give 40 qts. of 38%. Hence, to make 20 cans: 

31.0 X 20 == 620 quarts 48% cream 
9.0 X 20 = 180 quarts 3.6% milk 

when mixed will give 800 qts. (20 cans) of 38% cream. 

Other cream standardizing problems may be worked out 
in like manner. 

In each case, after the proper proportions are thoroughly 
mixed, samples should again be taken and tested to confirm the 
result. 



45 



QUESTIONS AND ANSWERS ON TESTING 

At regular intervals, the officials of the various State Depart- 
ments of Agriculture conduct examinations for those wishing 
to obtain licenses to act as milk testers at places where milk is 
purchased on a butter fat basis. At these examinations, correct 
answers in writing to a set of questions are usually required. 

The following questions are representative of those that may 
be asked at such an examination. Each question has been 
answered by Mr. Harold W. Gray of the Borden's Farm Products 
Co. (Inc.), Laboratory Staff. These answers amply serve as 
models of proper answers for the prospective candidate at an 
examination: 

1. 

Ques. Name the principal substances and the percent of 
each in milk of average composition. 

Ans : The principal substances and the percent of each in 
milk of average composition are as follows: 

Water 87.0% 

Sugar 5.0% 

Fat 4.0% 

Casein 2 . 6% 

Albumen 0.7% 

Ash 0.7% 



100.0% 
2. 

Ques: Describe briefly how the Babcock test for fat in 
milk is made. 

Ans : The milk to be tested is very carefully mixed by pour- 
ing from one dish to another. If the tester is dealing with a 
composite sample, the milk must be warmed to approximately 
90 degrees F. previous to mixing. 17.6 c.c. of the sample are 
then taken and discarded to rinse out the pipette. The second 
amount is kept, and placed in an 8% milk bottle. This bottle 
is then placed in a water bath having a temperature of 60 degrees 
F, and left until the milk has assumed the temperature of the 
water. The sulphuric acid to be used should be cooled in like 

46 



manner to the same temperature as the milk. Then 17.5 c.c. 
of the acid are measured and added to the milk. The sample 
is carefully agitated with a rotary motion until all the solids — ^not 
— fat are destroyed. The test bottle is then placed in the machine 
and whirled for five minutes at the proper speed. Water at 150 
to 160 degrees F. is then added to the base of the neck; the 
sample is again whirled for two minutes and additional water 
at the same temperature as before is added until the fat has 
risen so as to be measured. The machine is then run for one 
minute. After this, the test bottle is immersed in a water bath 
at a temperature of 135 to 140 degrees F. for three minutes, 
care being taken to completely surround the fat column. The 
restdt is then quickly read by means of dividers or calipers. 

3. 

Ques: What changes in the milk are brought about when 
the sulphuric acid is mixed with the milk in the Babcock test? 

Ans : When sulphuric acid is mixed with milk in the Bab- 
cock test, the following changes take place: 

(a) All the solids — not — ^fat are destroyed. 

(b) In accomplishing this, much heat is generated, which 

keeps the butter fat in a liquid state. 

(c) The specific gravity of the liquid surrounding the butter 

fat is increased, which makes it much easier for 
the fat to rise. 

4. 

Ques : What special precautions are necessary in preparing 
composite samples for testing? 

Answer : 

(a) Care in handling composite sample jars. 

(b) Place jars in a vat or tub containing water between 

90 and 100 degrees F. (Do not exceed 100 degrees 
F.) Allow the jars to remain in this bath until 
the milk has assumed the temperature of the water. 
The tester should be careful not to have too much 
water in the container, thus causing the jars to 
^ overturn. 

(c) Shake gently until all the cream is washed down, 

being careful not to chum the milk. 
47 



(d) Mix well the milk by pouring from one dish to another. 

(e) Draw up the first pipette of milk and let the contents 

run back into the jar. This is done to rinse the 
pipette. Keep the second amount — 18 grams 
(17.6 c.c). 

(f) Hold the test bottle and pipette at an angle and let 

the milk run into the test bottle. This bottle 
should be carefully marked to identify the dairy- 
man's sample. 

(g) Next, place the test bottle containing the sample in a 

water bath of about 60 degrees F., and allow it to 
stand for several minutes before adding the acid. 

5. 

Ques: How does the fat in a completed Babcock test 
indicate : 

(a) that the acid was too strong. 

(b) that the temperature of the milk and acid were too 

high when they were mixed together. 

(c) that the acid was too weak. 

Ans : (a) Black specks and charred particles at the bottom 
of the fat column indicate too strong an acid or too little agitation. 

(b) A cloudy fat column is caused by high temperature 
of acid and milk when mixed. 

(c) Too weak acid will give a very pale-colored fat column. 

6. 

Ques: At what points in making a Babcock fat test is. 
temperature of importance, and why? 

Ans: Proper temperature is very essential to secure 
accurate readings in the Babcock fat test. Acid and milk 
should always be mixed at an approximate temperature of 60 
degrees F., because the re-action at this point will give the 
proper colored fat column and the destruction of all solids — not 
— ^fat, providing acid is at the proper strength. In the next 
place, water should be added during the running of the test at a 
temperature of 150 to 160 degrees F., to properly wash down the 
fat and enable it to rise. Water at a lower temperature will 
give a thick, muddy-colored column, and will tend to harden 
the fat, which must be kept in a liquid condition. Again, before 

48 



reading the results, the test bottles should be taken from the 
machine and immersed for three minutes in a water bath at a 
temperature between 135 and 140 degrees F. This is done for 
the reason that the graduated portion of an 8% milk test bottle 
holds 1.6 c.c. Melted butter at 140 degrees F. has a specific 
gravity of .9, giving 1.44 grams (1.6 X .9 equals 1.44), which is 
8% of 18 grams (18 X .08 equals 1.44), the amount of the milk 
taken. If a 10% milk test bottle is used, the same results are 
obtained as follows: The graduated portion holds 2 c.c; the 
specific gravity of melted butter at 140 degrees F. is .9. 2 x .9 
equals 1.8 grams. 10% of 18 grams equals 1.8 grams. 

7. 

Ques: Describe briefly the method of taking, preparing, 
and testing a sample of cream. 

Ans: The cream in a can or vat should be thoroughly 
agitated by stirring before selecting the sample. If a composite 
from several cans is to be secured, take an equal amount from 
each can and place this in a receptacle. Warm the sample to 
approximately 80 degrees, and mix again by pouring. Weigh 
into a 50% cream test bottle, 9 grams of the liquid. Then cool 
this amount to 60 degrees. Add an equal amount of water at 
the same temperature. To the sample, add about 15 c.c. of 
sulphuric acid (temperature 60 degrees F.) Shake thoroughly 
with a rotary motion. After this, at once place the test bottle 
in the machine and run at the proper speed for five minutes, two 
minutes, and one minute, adding water (150 to 160 degrees F.) 
as in a whole milk sample. Then place the test bottle in a water 
bath (135 to 140 degrees F.) for three minutes, taking care to 
completely surround the fat column. Before reading the results, 
add about three drops of glymol to flatten the meniscus. This 
should be allowed to trickle down the sides of the bottle. Do 
not drop the glymol directly on the fat. 

8. 

Ques : At what points at the upper and lower ends of the 
fat column should the percentage reading be taken, 

(a) for milk (b) for cream 

Ans : (a) The fat column for milk should be read from the 
lowest point of the bottom curve to the extreme upper point of 
the top curve. 

49 



(b) Use glymol to flatten the curve and read from the 
lowest point of the bottom curve to the line of demarkation 
between the glymol and the fat column. In other words, read 
to the bottom of the red line. 

9. 
Ques: If you were given a set of Babcock test glassware, 
how would you know that you could legally use it for testing 
milk, where the milk was sold on the basis of the fat percentage 
that you found? 

Ans : If a person or concern buys or sells milk on the basis 
of the fat therein contained, all glassware used in the Babcock 
test must be calibrated by the New York State authorities at 
the Geneva Experimental Station, Geneva, N. Y. Such glass- 
ware is marked " S. B. " (State brand). The use of un-calibrated 
glassware is illegal. (Note: Most states have similar regu- 
lations regarding the calibration of glassware.) 

10. 

Ques: Name the precautions necessary for taking and 
keeping composite samples in good condition. 

Ans : Composite samples should be taken from ti^e weigh 
tank. After the supply has been dumped into the weigh tank, 
take a 1-oz. dipperful and place the contents into a jar, well 
stoppered and carefully labeled to identify the patron. One 
corrosive sublimate tablet (two in summer) should be used for a 
preservative. Carefully shake with a rotary motion. This 
should be done twice daily before and after delivery. The 
samples should be kept in a cupboard away from the light, in a 
cool place, and locked, except at the time of receiving the milk. 
As each additional amount is added from day to day, great care 
should be used not to wash up the cream on the sides of the jar. 
Never pull over a composite jar, but lift it straight from the shelf. 
Shake well, unstopper, add the sample, shake again, and place 
the jar in its proper place. If a weigh tank is not in use, thor- 
oughly mix the milk with a stirrer or agitator and, by means of a 
"milk thief, " take a proportionate amount from each can of the 
individual dairy by touching the bottom of the can with the 
thief. Transfer from each can such a sample to a small pail. 
From this pail, take one 1-oz. dipperful, and place the contents 
into the test jar. 

50 



Samples should be kept for a period of ten days after running. 
These should be placed in a cool place away from the light. 
This action is to comply with the New York State law regarding 
the holding of composite samples, 

11. 

Ques; What should be the specific gravity of the acid 
used in the Babcock test? 

Ans: The specific gravity of sulphuric acid used in the 
Babcock test should be between 1.82 and 1.83, preferably 1.825. 
The proper straw-colored fat column is the best indication of the 
proper strength of the acid. 

12. 

Ques: Why must cream be weighed into the Babcock test 
bottle in place of measured like milk? 

Ans: Since cream has a larger percentage of butter fat 
than milk, it must be weighed into the Babcock test bottle in 
place of measured, because otherwise it would cling to the inside 
of the pipette. For this reason, 9 grams — the amount required — 
would not be delivered. Again, the weight of the cream decreases 
as the percent of the fat increases. Separated cream contains 
air bubbles and ripened cream gases of fermentation which also 
decrease the weight. 

13. 

Ques: At what speed should the disks of Babcock centri- 
fuges revolve when they have the following diameters: 

(a) 10 inches (b) 16 inches (c) 20 inches 

Ans: (a) 10 in. — 1100 revolutions 

(b) 16 « — 850 

(c) 20 " — 760 " 

The complete scale for reference: 

10 in. — 1100 revolutions 



12 


u 


—1000 


14 


u 


— 925 


16 


u 


— 850 


18 


u 


— 800 


20 


u 


— 760 


22 


u 


— 725 


24 


u 


— 700 



51 



The following pages are to be reserved for the inserting of 
such additional information on testing that will from time to time 
be sent to all branches. These additions will be of proper size 
to be pasted on specified blank page of this book. 



52 



53 



54 



55 



56 



57 



58 



59 



6a 



61 



62 



63 



64 



65 



66 



67 



68 



69 



70 



71 



72 



73 



74 



75: 



76 



77 



BACTERIAL CONTROL 
DIRECT MICROSCOPIC OR BREED METHOD 

In order to provide a method of analysis that woiild permit 
of the rapid bacteriological examination of a number of milk 
samples without evolving too complicated a procedure, and thus 
minimizing the cost of analysis per sample, the direct micro- 
scopic method was introduced by Dr. Robert S. Breed of the 
New York State Experiment Station at Geneva. 

In commenting on the Breed Method, the last report of the 
Committee on Standard Methods of Bacteriological Analysis of 
Milk states: 

''For the purpose of rapidly dividing raw milk into a series 
of grades, in such a way that the results can be obtained in the 
quickest possible time, the direct microscopic method is ex- 
tremely useful. The use of the direct microscopic method is 
particularly valuable at the dairy end of the milk route, where 
the farmer wishes to know the kind of milk he is producing, or 
the purchaser at the shipping station wishes to know the kind of 
milk he is receiving from the farmer." 

DETECTION OF HIGH COUNT DAIRIES 

The latter consideration is the one that applies to us in our 
efforts to meet the Department of Health regulations as to bac- 
teria standards. The maintenance of a satisfactory bacterial 
count of the mixed raw milk will be dependent largely on our 
ability to detect and apply corrective efforts on those dairymen 
who chronically exceed the prescribed bacterial standard. It 
is this type of dairy, habitually delinquent in methods (usually 
unclean utensils or indifferent cooling) that supplies sufficient 
contaminating influence in its milk so that when mixed in the 
storage vat at the milk station, it raises the entire receipts be- 
yond the prescribed bacterial standards. Accordingly, our mis- 
sion lies in detecting high count dairies, and here the Breed 
method is particularly useful. 

78 



The following are given as directions for preparing dried 
smears by the Breed method for forwarding to laboratory for 
examination and report of results. It is absolutely essential that 
these directions be closely followed : 

COLLECTION OF SAMPLES 

Samples are to be taken once every two weeks on specified 
day as per schedule, in the sterilized four-dram vials. A can 
of the night's milk of each patron is to be sampled, the same to 
be thoroughly stirred with a thoroughly clean regulation can 
stirrer. The can stirrer is to be immersed first in a can of clean 
water and then allowed to remain between samplings in another 
can of boiling water before being used to stir the night's milk of 
another patron. The sample is to be taken from the stirred can, 
as the can is being poured into the weigh tank, catching the 
sample when about half of the milk has been poured from the 
can. The metal cap should be replaced immediately, and the 
vial numbered with the dairy number that it represents. The 
vial should then be placed in a sample tray that has been pro- 
vided for that purpose, in its proper numerical position in the 
tray. 

SAMPLE TRAY 

The sample tray regularly supplied will accommodate 70 
vials. The outer case of the sample tray should at all times 
be liberally supplied with finely crushed ice and water so that 
practically the entire vial will stand in ice water. 

In most instances the smears from the samples can be pre- 
pared best in the early afternoon, in which event, precautions 
should be taken to see that the tray is well provided with ice, 
the cover placed over same, and the tray put away in a cool 
place. 

Always be sure that the tray is well provided with ice, and 
that the samples are standing in ice water up to the time of mak- 
ing the smear of each individual sample. 

MAKING OF SMEARS 

y. The remainder of the technique of the Breed method con- 
sists of accurately measuring 0.01 c.c. of each sample, trans- 
ferring this amount of milk by means of a small pipette to a 

79 



clean glass slide, distributing the milk evenly over one square 
centimeter of the slide by means of a stiff needle, and then allow- 
ing the smear to dry in a moderately warm, level place. The 
slides are then ready to be shipped by parcel post to the labor- 
atory, where they are properly treated to remove the fat, after 
which they are stained and examined under a high power micro- 
scope. 

GUIDE SLIDES 

In order to make the smears conveniently a guide is fur- 
nished, containing a number of accurately measured square cen- 
timeter areas, this guide slide being placed under the plain slide 
on which the smears are to be mounted. The plain slides have 
etched margins to permit lead pencil markings of dairy number 
which each smear represents. 

Smears should be made in numerical order, each sample 
vial being allowed to remain in its proper place in sample tray 
of ice water until smear is made. 

MEASURING THE MILK FOR SMEAR 

The sample vial should be thoroughly shaken and the special 
0.01 c.c. pipette inserted below the mark of graduation on same. 
Ordinarily capillary attraction will draw the milk slightly above 
the graduation mark. The finger is then placed over the upper 
end of the pipette as it is withdrawn from the vial. By means 
of a clean towel the milk adhering to the outside and tip of the 
pipette is then wiped off. If the milk still remains above the 
graduation mark of the pipette it may be brought down by 
gently touching the tip of the pipette with the clean towel at 
the same time slightly releasing the finger over the upper end 
of the pipette. The milk must be brought exactly to the grad- 
uation mark. 

By gently blowing on the pipette the milk should then be 
deposited on the plain glass slide over one of the centimeter 
squares. By means of the needle that is provided, the milk is 
then smeared out evenly until it entirely covers the one square 
centimeter space as indicated by the guide slide. (The number 
of the dairy should then be marked on the etched margin of the 
slide opposite the smear). When a number has been assigned 
on the milk register to a dairy that is not delivering milk, a 
- 80 



I 



vacant place should be allowed on the slide, thus alloting twelve 
dairies as carried on the milk register to each sHde. Further- 
more, the particular number assigned to a dairyman should not 
be changed at any time, as the records that will be kept and 
compared from time to time will be carried on the basis of dairy 
number only. 

RINSING PIPETTE 

Before proceeding to the next sample, it is necessary to clean 
the pipette and this can be accomplished by rinsing it in clean 
warm water. The needle should also be rinsed in the clean 
water and wiped dry on the clean towel. After the work on two 
slides has been completed — that is, 24 smears prepared — the 
rinsing water should be discarded and a fresh supply used. The 
procedure as above outlined should be continued, placing twelve 
smears on each slide and keeping the smears in numerical order, 
until all the samples have been thus prepared. 

DRYING SMEARS 

When the twelve smears have been prepared, the slide 
should be placed in a moderately warm, level spot so that 
they will be entirely dry in approximately ten minutes. This 
feature is important, inasmuch as there is danger of increase in 
number of bacteria up to the point when the milk is entirely dry. 
A convenient method to bring about prompt drying is to lay a 
board over a radiator and place the slides on this board. If the 
slides are placed directly upon a hot surface they will crack and 
peel off. However, drying must be prompt and should always 
be accomplished in from ten to fifteen minutes. While prepar- 
ing for the next smear, place the pipette in the rinsing water. 
Before taking pipette sample, blow out the surplus water, then 
rinse a second time by drawing in a fresh supply of water, again 
blowing this out. Be sure the pipette is absolutely free from 
water before placing same in milk vial. 

LABORATORY EXAMINATION 

The slides containing the dried smears are now ready to be 
placed in the special mailing box to be sent by parcel post to the 
laboratory for proper treatment and examination. A small wad 

81 



of paper should be placed between the upper edges of the slides 
and the under side of the box cover, so as to hold the slides se- 
curely in place and thus prevent breakage in transit. A report 
will be sent promptly to the forwarding branch in which the re- 
sults will be listed under "Report of Results." At the same time 
another mailing box, containing the proper number of clean slides 
will be sent to the branch to be used for the next set of smears. 

CLEANING AND STERILIZING VIALS 

Immediately after the smears are prepared, the milk should 
be emptied and the vials washed in the following manner : Rinse 
both caps and vials several times in cold water. Prepare a solu- 
tion of soap powder in hot water. Thoroughly wash each vial 
and cap in the soap solution, using a test tube brush. Rinse sev- 
eral times in clean, hot water. Invert the vials, with cap still 
removed, until thoroughly dry. When dry, screw cap on each, 
and sterilize by live steam in box sterilizer for at least thirty 
minutes. The day before samples are to be taken, vials should 
be sterilized a second time, again giving them at least a thirty 
minute exposure to the live steam. A small wire basket is the 
most convenient container for sterilizing vials. 

REPORT ON RESULTS 

In the report sent from the Laboratory, the designations 
"A," *'B" or "C" will be given opposite each of the dairies from 
whose milk smears were prepared. Specific counts are only 
given for those dairies that fall in the "B" and "C" classes. 
The three designations will represent as follows: 

A. — Dairies whose count does not exceed 100,000 per c.c. by 
the Breed method. Such milk will be considered entirely satis- 
factory from a bacteriological standpoint. 

B. — Dairies whose count falls between 100,000 and 500,000 
per c.c. Such milk is considered only fair from a bacterial stand- 
point. 

C. — Dairies whose count is in excess of 500,000 per c.c. Such 
milk is considered unsatisfactory in itself and also a source of 
danger in the contaminating influence it exerts on the "A" and 
"B " dairies when mixed with them in the raw milk storage tank. 

82 



The report will also contain a summary in which the num- 
ber of "A," "B" and "C" dairies will be totaled, and the per- 
centage of each among the whole number of dairies delivering 
at the plant will be computed. From these percentages a "bac- 
terial score" will be given, 100 being a perfect score, and in 
which event it would be necessary to have all the dairies deliv- 
ering to a plant in the "A" group. 

A sample of such summary is here given : 





Number of 


Percent of 


Bacterial 




Dairies 


Dairies 


Score 


A 


45 


85 




B 


3 


6 


88 


C 


5 


9 





The bacterial score is merely a convenient way of reducing 
the results into one concrete figure, thereby permitting com- 
parison of the results of one set of smears with those obtained 
at an earlier date. It also permits the comparison of the milk 
supply of one locality with that of another locality. The bac- 
terial score is obtained in the following manner: 

By allowing 1 point for each percent of "A" dairies. 
(I (f n ^ " " " " " **B" " 

II a r\ a a n (c u ttr^i} n 

It shotdd be borne in mind that the above system of divid- 
ing the milk into "A," "B" and "C" groups by means of the 
Breed method and reducing the results thus obtained to a bac- 
terial score, has no official recognition, and that it is merely a 
system devised to meet the desire of our Company to maintain 
at all times a satisfactory bacterial content of their product. 
The designations "A," "B" and "C" are not intended to place 
these dairies in any particular grade of market milk, but are 
merely assigned to them as an indication of whether or not they 
are producing milk that is entirely satisfactory from a bacterial 
standpoint. 

CORRECTIVE WORK 

When a report similar to that above described is received, 
it is expected that a personal visit will be made to each dairy 
listed under the "C" designation, the object being to determine 

83 



the cause of the high bacterial count. Here a knowledge of the 
factors that bring about a low bacterial count milk will be of 
value to the inspector. A survey of the dairy premises and a 
heart-to-heart talk with the dairyman will usually bring out the 
evidence that one of the fundamental requirements for a low 
bacterial count milk is being violated. 



ESSENTIALS FOR PRODUCING CLEAN MILK WITH A 
LOW BACTERIA COUNT 

MILKING. — Clean cows; clean, dry hands; narrow top pail; 
clean strainer. 

COOLING. — Plenty of ice or cold water below 50 degrees 
F. ; clean milk house. 

STERILIZING. — Rinse pails and strainers with clean, cold 
water immediately after milking; wash with brush and Alkali 
Powder; rinse with clean water; sterilize with boiling water. 

These are the features in particular that should be "talked 
up" to the "C" dairymen, for it is usually irregularities in some 
of these that result in high bacterial counts. Consequently, the 
"follow up" work on the "C" dairies is largely one of education, 
every opportunity should be taken to impress on the dairymen's 
minds the importance of the fundamentals of low bacterial count 
milk, especially in regard to clean utensils and proper cooling. 

The "B" dairies should also be visited as outlined above, 
inasmuch as there is some irregularity in each, which may, if 
further neglected, result in their dropping to "C." 

As in the past, every effort should be made to encourage 
the dairymen to properly equip their dairies to meet these fun- 
damental requirements and the milk house with its cooling vat 
and space to store dairy utensils is an absolute necessity. This 
holds true for every other feature of equipment and practice in 
methods that our Company has for years advocated, inasmuch 
as the average dairyman's ability to produce clean milk — that is, 
milk of low bacteria count — is largely dependent on the condi- 
tions under which he performs his daily work, 

84 



In summarizing, it may be said that the object of the above 
method of bacteria control is : 

1st. To determine by the most convenient method known, 
the approximate bacterial count of the milk of each of our 
patrons. 

2d. To divide the results into suitable groups and to supply 
this information to our representatives as a guide to them in ap- 
plying corrective work. 

3d. To impress upon the dairymen the fundamental require- 
ments of low bacterial count milk. 

4th. To detect these dairymen who are habitually delivering 
milk of high bacterial count. These men make it possible for 
the supply as a whole from any one plant to be shut out by the 
Department of Health from the market for which it is intended. 



85 



STANDARD BREED METHOD TECHNIQUE 

The material in preceding pages is drawn up in the form 
of complete directions for the preparation of Breed smears, where 
such smears are prepared by local factory representatives. The 
directions are intended to be minute in each detail of the work, 
so as to lead to standard and uniform practice in this work. 
When smears are so prepared, the examination and microscopic 
work is carried on by a central laboratory, where the prepared 
smears are shipped by parcel post. 

For the trained man who may go into the field equipped with 
microscope and other necessary apparatus and solutions, the 
following procedure is given : 

" The practice of counting the bacteria in milk by means of the 
microscope has been, in the last few years, coming somewhat rapidly 
into use, and offers several advantages: 

ist. It is extremely rapid, making reports possible within a 
very few hours. 

2d. It is simple and requires little apparatus. 

jd. It gives a means whereby the actual number of bacteria can 
be determined, and it also gives some idea as to the kinds of bacteria 
present. 

On the other hand, it requires considerable experience to obtain 
reliable results, and because it does not distinguish the living from 
the dead, it is not applicable at the present time to the study of pas- 
teurized milk. Its manifest advantages for some purposes makes 
it certain, however, that its use will extend, and for this reason it is 
included in these Standard Methods. 

Various methods of the microscopic study of milk have been 
described, but that which may be called the direct microscopic exam- 
ination of milk is the simplest and most reliable, and is recognized 
in this report as Standard. It is as follows: 

Samples. Milk samples collected as above described may be 
preserved by icing and handled as in the case of the plate method. 
All samples on which cream has risen to the surface must be vigor- 
ously shaken before preparations are made from them. 

Apparatus. In addition to a microscope and ordinary micro- 
scopic slides, stain, etc., the only special apparatus required is a 
pipette which measures i/ loo c.c. The most convenient form of 
pipette is the straight capillary pipette, calibrated to deliver i/ lOO 

86 



c.c, the graduation mark being i}^ to 2}4 inches from tip. Such 
pipettes are now for sale by manufacturers, and can be easily 
obtained. Only a single pipette is needed in making a series of 
tests, provided this is kept clean while in use. In this kind of work, 
cleanliness rather than sterilization is required. Clean towels may 
be used for wiping the exterior of these pipettes, while their bores 
may be kept clean by rinsing them in clean water between each sam- 
ple. The small amount of water left in the tube may be rinsed out 
into the milk sample under examination. This method of procedure, 
while adding a small number of bacteria to each sample, introduces 
only a theoretical error, tests showing that such bacteria cannot sub- 
sequently be detected, and make no difference in the final result. 

Preparation of Smears. One one-hundredth c.c. of milk or 
cream is deposited upon a clean glass slide by means of the pipette 
above described. By the use of a clean, stiff needle, this drop of 
milk is spread over an area of one square centimeter. This may be 
most conveniently done by placing the slide upon any glass or paper 
ruled into areas one centimeter ■ square. These marks showing 
through the glass serve as guides. After uniform spreading, the 
preparation is dried in a warm place upon a level surface. In order 
to prevent noticeable growth, this drying must be accomplished within 
five to ten minutes- but excessive heat must be avoided or the dry films 
may crack and peel from the slides in later handling. 

After drying, the slides arc to be dipped in xylol {gasolene may 
be used) for one minute, then drained and the slides dried. They 
are then immersed in go% grain alcohol (or denatured, or wood al- 
cohol) for about ij seconds, and then transferred to a fresh aqueous 
solution of methylene blue. Old or unfiltered stains are to be avoided, 
as they may contain troublesome precipitates. The slides remain 
in this solution from lo to 15 seconds, and then should be trans- 
ferred immediately to a jar containing clean water to remove the 
excess stain. When this procedure is followed carefully, subsequent 
decolorization with alcohol is unnecessary. When properly stained, 
the general background of the film should be of a light blue tint. 

The slides should be allowed to air dry by standing them in a 
vertical position. When dry, they are ready for examination. 

STANDARDIZATION OF THE MICROSCOPE 

The microscope to be used must be adjusted in such a way that 
each field of the microscope covers a certain known fraction of the 

87 



total square centimeter^ s area. This procedure is simple, with the 
proper materials at hand. The microscope should have a t.q mm. 
(-jig- inch) oil immersion objective, and an ocular giving approximately 
the field desired, and should preferably be fitted with a mechanical 
stage. To standardize the microscope, place upon the stage a stage 
micrometer, and by the selection of oculars or adjusting the draw 
tube, or both, bring the diameter of the whole microscopic field to 
,202 mm. When so adjusted, the microscopic field will cover almost ex- 
acily 1/ joo,ooo of a cubic centimeter of the milk {actually 1/^02,846). 
This means that if the bacteria in one field only are counted, the 
number should be multiplied by joo,ooo to <:ive the total number in 
a cubic centimeter. 

(From "Standard Methods A. P. H. .1.") 

SIMPLIFIED METHOD OF OBTAINING APPROXIMATE 
BACTERIA COUNT BY MEANS OF BREED METHOD 

Examine fifteen fields on each smear. 

Count the number of groups or clumps, as well as individual 
isolated bacteria that are present. 

Record this number on examination sheet. 
Designate the final result with the following, indicating as 
A, B and C: 

to 5 clumps inclusive in 15 fields — A (100,000 per 

c.c. or less) 
6 to 25 " " " " " — B (100,000 to 

500,000 per c.c.) 
Over 25 " " " " " — C (over 500,000 

per c.c.) 

When bacteria are so numerous that accurate count cannot 
be made, show the result as "TNC" (too numerous to count). 

When all the examinations are made, and above grades have 
been given, group results in the form of a summary, as follows: 

Count the total number of A, B and C dairies. 
Compute the percentage of A, B and C. 

Allow 1 point for each percent of A dairies. 

<< 1/ ii a <e u "D tc 

II f\ <( ii (( a /"» a 

The sum of these points gives a bacterial score. 

88 



Report results of 5 or less clumps in 15 field simply as "A." 

In those cases where the number of clumps are more than 
5 in 15 fields, the actual count per c.c. in each case may be ob- 
tained by multiplying the number of clumps in 15 fields by 20,- 
000, For example: 

If 21 clumps are found in 15 fields, the bacteria per c.c. 
would be (21x20,000) 420,000 per c.c. 

(Note: The examination of 15 fields is sufficient for routine 
work, where a classification is merely desired.) 

A description of the technique and comments on the Breed 
method and its application by Joseph Race in a recent work 
(1918) follow: 

"In some of the comparative experimental work reported 
by Conn, a series of bacterial counts was made by Breed, and 
this was supplemented in a further series by the inclusion of 
Brew, a co-worker with Breed. These experimenters made mi- 
croscopical counts on the samples plated by other observers, 
and Conn considered that when the groups of organisms only 
were counted, the count agreed somewhat closely with the plate 
count. The details of Breed's process are as follows: 0.01 c.cm. 
of milk, from a well-shaken sample, is measured out by means 
of an accurately calibrated special pipette and deposited on a 
glass slide on which an area of 1 square centimeter has been 
previously marked out. The drop is evenly smeared over this 
area with a stiff needle and gently dried at about 50 degrees C. 
The slide is then placed in a Coplin staining jar containing xylol 
or gasolene to remove the fat, and, after drying, fixed in alcohol 
(70 to 95%). Immediately afterwards the smear is stained with 
1 per cent aqueous methylene blue and finally decolorized to a 
light blue in 95% alcohol. The microscopical examination is 
made with a -^ inch oil immersion objective. In order to find 
the factor for converting the number of organisms per field into 
organisms per cubic centimeter the diameter of the field is de- 
termined with a stage micrometer. The factor is then calcu- 
lated from the formula: 

X 

X 100 = y, 



77R' 

where y is the factor sought, x, the area of the smear in square 
millimeters and R the radius of the field. 

89 



In practice it is convenient to pull out the draw tube until 
the area of the fields is of such a value as will give a value to y 
having as many ciphers as possible. The following are the most 
satisfactory : 

When R = 0.080 m.m. , y = 500,000 
When R = 0.089 m.m., y = 400,000 
When R = 0.101 m.m., y = 300,000 

When the desired result is obtained, the position of the 
draw tube is noted and always set at this point in future exam- 
inations. In order to get results comparable with the plate 
method, only the groups or clumps, together with isolated bacilli 
are counted; individual cocci, diplococcus or streptococcus chains, 
and rod forms where the plane of division shows clearly, are 
counted as individuals. The number of fields to be examined 
must be determined by the frequency of the organisms. It is 
obvious that with a factor of 300,000 to 500,000, this method is 
of the greatest advantage when the count averages one clump 
or more per field; with high-grade milks under 10,000 bacteria 
per c.c, the number of fields to be examined would be so large, 
if reasonable precision is to be obtained, as to consume as much 
time as the plate count method. Dead bacteria are counted 
with the living, so that this process is not applicable to pasteur- 
ized products ; it would, however, be of advantage in determining 
the quality before pasteurization. A collateral advantage of 
this method is that in addition to the quantitative estimation 
of the bacteria, a cell count can be made at the same time and 
information obtained regarding the bacteria flora. 



90 



The following pages are reserved for additional information 
that will be sent out on bacterial control. 



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